Doubled walled plastic bag



United States Patent [72] Inventors WilliamJ. Clayton Fairport; RobertJ. Miller; Clair C. Smith, Holcomb, N.Y. [211 App]. No. 816,429 [22]Filed Dec. 16, 1968 [45] Patented Dec. 29, 1970 [73] Assignee Mobil OilCorporation a corporation of New York Division of Ser. No. 442,323, Mar.24, 1965, Pat. No. 3,466,212.

[54] DOUBLED WALLED PLASTIC BAG 2 Claims, 12 Drawing Figs.

52 us. c1 229/55, 150/05 [51 Int. Cl B65d 33/02 501 FieldofSearchQ..229/55,53; 150/053,?

[56] 2 References Cited UNITED STATES PATENTS 3,084,984 4/1963 Adler229/55 3,269,643 8/1966 MCDOWCII..... 229/55 3,346,173 10/1967 Smithetal229/55 Primary Examiner-David M. Bockenek Attorneys-Oswald G. Hayes,Donald L. Dickerson and James D. Tierney ABSTRACT: A double-walledthermoplastic bag comprising a flattened tube formed from athermoplastic laminate, the tube being sealed at one end and the doublewalls of the bag being heat sealed together along a plurality ofintersecting heat sealed areas.

PATEmz-inumsmm I 3.550.839

saw 1 OF 4 F/QI/ INVI'IN'I'OHS WILLiAM J.CLAYTON ROBERT J MILLER CLAIRC. SMITH PATENTEB DEB29197U WI CLAYTON I LER CL TH IPAIENIEUUEBEQIBYC3,550, 39

SHEET 3 [IF 4 INVIa'N'I'U/IS WILLIAM J. CLAYTON ROBERT J. MILLER CLAIRC. SMITH PATENTED 05029 I978 INVI'JN'I'ORS WILLIAM J. CLAYTON ROBERT J.MILLER CLAIR C. SMITH DOUBLED WALLED PLASTIC BAG CROSS REFERENCE TORELATED APPLICATION This application is a division of copendingapplication Ser. No. 442,323, filed Mar. 24, 1965, now U.S. Pat. No.3,466,2l2.

The present invention relates to embossed thermoplastic films,Iaminations of embossed thermoplastic films and, more particularly, tomethods for manufacturing such film products.

In certain techniques disclosed in the prior art, embossments have beenformed upon the surface of single or multiple layers of film products byemploying embossing rolls, or the like, which serve to mechanicallyimprint a desired pattern upon the surface of a film by a physical,permanent distortion of the film surface. Heat is sometimes employed insuch embossing operations to soften the plastic material therebyfacilitating the impression of a desired pattern into the surface of afilm and also insuring, to a degree, a permanent type embossment of thefilm surface.

It is also known in the prior art to form embossed laminar products.This may be accomplished by well known vacuum forming techniques wherebya single layer of film is subjected to vacuum application in selectedareas, resulting in a plurality of concave distentions of the filmsurface and, subsequently, a smooth film is applied to one or both sidesof such a vacuum embossed film to form an embossed, laminar structure.Generally, such a procedure is time consuming, the vacuum being appliedto the base sheet of film in successive, incremental, stages and thelamination procedure likewise requiring separate processing steps.

In accordance with the teachings of the present invention, film may beformed into embossed structures and embossed,

laminar, structures utilizing an extremely simple and efficientprocessing technique.

Additionally, the process of the present invention may be employed toproduce embossed, laminar, products which have air bubbles encapsulatedtherein, in a predetermined, pattemed, configuration.

For a more complete understanding of the process of the presentinvention, reference may be had to the accompanying drawings wherein:

FIG. 1 is a side view in elevation, largely diagrammatic, of anapparatus suitable for practice of the process of the present invention.

FIGS. 2 and 3 are similar to FIG. 1, illustrating apparatus useful toproduce embossed, laminar products in accord with process of the presentinvention.

FIG. 4 is an elevational view on an enlarged scale, partly in section,of a type of raised, patterned, surfaced cylinder which may be employedin the process of the present invention.

FIGS. 5, 6, 7, 8, 9 and 10 are plan and cross-sectional views, partlybroken away, illustrating various structural configurations of theembossed thennoplastic materials produced in accord with the process ofthe present invention.

FIGS. 11 and 12 are illustrations of various types of bag structureswhich may be produced utilizing the embossed thermoplastic materialsmade in accord'with the process of the present invention.

In the practice of the present invention, use is made of a raisedembossing and sealing pattern 15, of substantial height and, forexample, of a height sufiicient to provide on the film surface adifference in elevation larger than is provided by normal printing orcoating of such a surface. Generally speaking, in the practice of thepresent invention the raised pattern I5 is at least 4 mils in height andmore preferably from about l0 to about 50 mils.

As illustrated in FIG. 1, film 11 from continuous film supply roller 12is fed under roller 13. Resilient surfaced (e.g. sponge) roller 13impresses film 11 onto the face of a continuously moving support, e.g. amoving belt or a rotating cylinder as illustrated by 14 in FIG. 1.Cylinder 14 is maintained at a constant temperature utilizingconventional techniques e.g. by the circulation of fluids therein suchas water, or by the employment of refrigerant gas-containing coilsinserted therein, or any other suitable cooling means. The surface ofcylinder 14, is embossed in a desired raised pattern 15 such as arepetitive pattern of raised intersecting lines to form squares or, forexample, diamond shaped areas as illustrated in FIG. 4. As sponge roller13 impresses film 11 against the raised pattern carried upon the face ofcylinder 14, those portions of film 11, not in contact with portions ofraised pattern 15, since they are somewhat pliable, are distended andforced to assume a slightly concave configuration in those areasintermediate the 'raised pattern. As the film is rotated past the nipformed by sponge roller 13 and cylinder 14, the plurality of concaveconfigurations, impressed upon the film surface by sponge roller 13,remain. The film itself is now adhesively secured to the raised patterncarried by cylinder 14 by virtue of an infrared absorbing, (e.g.carbon-black impregnated) adhesive coating carried upon the surface ofraised pattern 15. As cylinder 14 rotates in a counterclockwisedirection, it carries film 11, now adhesively secured to raised pattern.15, past a source of heat energy 16. As a suitable source of heat, oneor more infrared emitting, quartzf-type lamps may be used, however forpurposes of the present invention it will be understood that any sourceof radiant heat energy may be employed such as e.g. electrically heatedcoils or the like. When film 11, thus secured to raised pattern 15, isexposed to' heat source 16, the film is selectively heated. Those areaswhich are in contact with raised pattern 15, by virtue of the presenceof the infrared heat-absorbing carbon-black material present in theadhesive coating, are rapidly heated to a relatively high temperature atwhich the thermoplastic becomes slightly molten, while those portions ofthe film not in contact with raised pattern 15 are heated to arelatively lower temperature sufficient to cause the slightly concavefilm portions within the cavity areas created by raised pattern 15 toassume a more pronounced concave configuration. As film 11, stilladhesively secured to raised pattern 15 carried on the surface ofcylinder 14, passes infrared heat energy source 16, by virtue of thecontinuous counterclockwise rotation of cylinder 14, it is fed under andaround separator roll 17, thereby stripping it from the adhesive coatingon the surface of raised pattern 15, and finally to windup roller 18 orto a further processing step.

, As an example of the process embodiment described above, a continuouslength of polyethylene film having an approximate gauge of 0.5 mil wasfeed from a supply roller 12 under a sponge surfaced roller 13 and intonipping engagement with a raised pattern 15 carried upon the surface ofa rotating cylinder 14, rotating at a speed of about 50 ft./min. Thepattern consisted of paperboard perforated to form a series ofintersecting raised lines, approximately 20 mils thick, therebyresulting in a series of diamond shaped configurations, as illustratedin FIG. 4. The surface of the pattern was coated with a IO-mil thicknessof a carbon-black impregnated adhesive composition. Rotating cylinder 14was maintained at a temperature of approximately 1 10 F. Subsequently,the film, adhesively secured to the adhesive coated surface of theraised pattern, was advanced by the rotating cylinder past two, 2400watt, infrared emitting, quartztype lamps. The lamps were positionedapproximately 6 inches from the surface of the film. Finally theembossed film product was stripped from the adhesive surface of theraised pattern utilizing a takeoff roller, as illustrated at 17 in FIG.1, and fed to a windup roller. FIGS. 5 and 6 are illustrations of theembossed thermoplastic film which is produced by the foregoing process.

In another embodiment of the process of the present invention, asillustrated in FIG. 2, laminar embossed films may be produced which mayconsist of two or more layers, bonded together in areas corresponding toraised pattern 15. As illustrated in FIG. 2, two films 11 and 11' arefed from individual supply rollers 12 and 12 and are subsequentlyimpressed in superposed relationship against the raised pattern 15carried on the surface of cylinder 14 as they are fed under spongeroller 13 and into the nip formed by sponge roller 13 and continuouslyrotating cylinder 14. This nipping action forces the film layers toassume a slightly concave configuration in those areas not supported byraised pattern on cylinder 14 and also causes that portion of thesurface of film layer 11, contacting raised pattern 15, to becomeadhesively secured thereto by virtue of the infrared absorbing adhesivecoating upon the surface of raised pattern 15. This adhesive fixation offilm layer 11, together with the plurality of concave configurationsimpressed upon the surface of both layers after passing through the nipformed by counterrotating rollers 13 and 14, secures the film layers infixed relationship with respect to one another and to rotating cylinder14, thereby facilitating further processing of the superposed filmlayers. Next, the film layers, by virtue of the rotation of cylinder 14upon which they are supported, are carried past the source of heatenergy 16 described above. When the film layers 11 and 11' become thusexposed to the heat energy emitting from source 16, they are heat weldedtogether only in those areas of the film layers which are backed by theraised infrared absorbing pattern 15,

which absorbs the radiant heat from source 16 and elevates thetemperature of the film in contact therewith causing film layer 11 tobecome heat sealed to film layer 11' along a pattern directlycorresponding to that of raised pattern 15, and thereby forming laminatestructure 19.

It has been found desirable to sometimes employ smooth surfaced roller20, extending across the face of rotating cylinder 14, to complete thesealing operation. Roller may be a Teflon-coated roller which isemployed to insure positive sealing of laminar layers 11 and 11' bypositively impressing them together in the nip formed by roller 20 androtating cylinder 14, after laminar structure 19 is carried by rotatingcylinder 14 past the heat energy source 16. Thereafter, laminatestructure 19 is fed under and around roll 17, thereby stripping it fromthe carbon-black impregnated, adhesivecoated surface of raised pattern15 and finally to windup roller 18 or to a further processing step suchas a slitting operation,

or; for example a bag making process.

' As illustrated in FIGS. 7 and 8, the face of laminate l9,

7 which was adjacent to raised pattern 15 during the sealing operation,has convex distentions in those areas which were not in direct contactwith raised pattern 15 during the heat sealing operation. The oppositeside of laminate 19 has less pronounced concave distentions on thesurface thereof in those areas opposite the concave distentions of thereverse side of laminate 19. Laminate structure 19 is furthercharacterized by having minute wrinkles formed immediately adjacent theareas of film layers which have been sealed, thereby imparting acrinkled appearance to the laminate structure, as in those areasillustrated at 21 in FIG. 5. Although this minute wrinkling may becaused by a combination of factors, it is theorized that it is mainly aresult of the differential heating of the surfaces of film layers 11 and11', those areas of the film supported by the carbon black impregnatedadhesive carried by raised pattern 15 being heated to a highertemperature than the film areas intermediate the raised pattern lines.These very minute wrinkles impart a unique appearance to the embossedlaminar structure, giving it a quilted appearance similar to that ofquilted textile materials.

In a particular example of the laminating and embossing processdescribed above, continuous lengths of polyethylene film, each with anapproximate gauge of 0.5 mil, were fed from supply rollers 12 and 12under sponge roller 13 and into nipping engagement with raised pattern15 carried upon the surface of a rotating cylinder, illustrated as 14 inFIG. 2. The cylinder was rotated at a speed of about 50 ft./min.Cylinder 14 was maintained at a temperature of approximately 80 F. Itshould be noted that the internal cooling of cylinder 14 is necessitatedby its continued exposure to heat source 16, which has a tendency toraise the temperature of cylinder 14 well above operable processconditions. The circulation of a coolant such as water through cylinder14 eliminates this undesirable rise of temperature. Next, thepolyethylene film layers were rotated past heat source 16. In thepresent example, two 2400 watt infrared, quartz-type lamps were used asa fed between the nip of a counterrotating Teflon-coated roller,

as illustrated at 20 in FIG. 2, to insure positive bonding of the filmlayers and finally the laminar product was stripped off theadhesive-coated surface of pattern 15 utilizing a takeoff roller, suchas 17 in FIG. 2, and fed to a windup roller. It has been found that thepositioning of roller l7, when it is removing the laminar product, isimportant in that i'tmust be positioned so that the lamination leavesthe embossing cylinder in a direction substantially perpendicular .tothe surface thereof, in order to avoid damage, such a permanentdistortion or delamination of the embossed laminar product. FIG. 3illustrates another embodiment of the process of the present invention.Film layer 11 is fed, from continuous supply roller 12, under spongeroller 13 and into the nip formed by sponge roller 13 and raised pattern15 carried on rotating cylinder 14. Film layer 11, now with slightconcave distentions on its exposed surface and adhesively secured to theinfrared absorbing adhesive coating of raised pattern 15, is carried, byvirtue of the counterclockwise rotation of cylinder 14, past heat energysource 16. As film layer 11 is exposed to the heat emanating from source16 the portions of film layer 11, not in contact with raised pattern 15tend to expandand assume a more pronounced concave configuration asdescribed above. a As film layer 11 passed heat source 16, a second film11' of tion by the carbon black present in the adhesive coating onraised pattern 15, in those areas supported by pattem 15.

As illustrated in FIGS. 9 and 10, there is no sealing together of thoseportions of the film layers which are not supported by the radiant heatabsorbing pattern 15, since they are relatively transparent to theradiant heat-sealing energy. Conversely, a pronounced separation ofthose portions of the film layers intermediate the raised pattern 15,occurs. This results from the fact that air has been entrapped in thearea between the concave distentions of film layer 11 and those portionsof film layer 11 covering these concave distentions. As a result theair, entrapped by the radiant heat sealing together of adjacent filmareas in contact with raised pattern 15 expands as a result of the heatfrom source 16 and forces the unsealed portions of the film layers toexpand thereby resulting in a plurality of entrapped air bubblesintermediate those areas of film adhesively secured to raised pattern15. The film laminate 19' may now be passed into a nip formed by smoothsurfaced roller 20 and rotating cylinder 14 to insure adequate sealingof the film areas supported by raised pattern 15, which nipping actionmechanically presses the film layers tightly together to insure positivesealing of those portions of the film layers supported on raised pattern15.

Thereafter, laminar film structure 19 is fed under and around roll 17,thereby stripping it from the carbon-black impregnated adhesive coatingof raised pattern 15, and finally fed to a windup roller 18 or tofurther processing steps.

It has been found that the volume of air which is encapsulated betweenthe film layers in those unsealed areas intermediate the intersectingseal lines may be varied by varying the location at which film layer 11joins film layer 11. If, as illustrated in FIG. 3, film layer 11' is fedonto the surface of film layer 11 at point P,, the amount of air whichis encapsulated between the unsealed film areas results in a laminarproduct having air bubbles on that surface of the lamination which wasin contact with raised pattern 15 during the forming operation. Theopposite surface of such a lamination, i.e. the side of the laminationnot in direct contact with raised pattern 15 is relatively smooth andflat. On the other hand, if film layer 11" joins film layer 11 at apoint P intermediate radiant heat sources 16 and 16. the size of theencapsulated bubbles in the final laminate product is greatly increased,both surfaces of the laminate structure having convex distentions as aresult of a relatively large volume of air being encapsulatedintermediate the opposing unsealed film layers adjacent the intersectingheat sealed areas, As is apparent from the foregoing, the volume of airentrapped between the film layers, and therefore the size of the airbubbles encapsulated in the final product, may be varied by varying thepoint at which film layer 11' is joined in-superposed relationship withfilm layer 1 l.

The adhesive composition, which is employed as a coating upon thesurface of raised pattern 15, may be any adhesive material which iscapable of adhesively securing film layer 11 in fixed relationship tothe surface of pattern 15, and which will allow for the ready removal ofthe finished embossed film product from the surface of raised pattern 15without destroying the film or its embossed surface design. Suitable forthat purpose is a carbon-black adhesive mixture of the followingcomposition:

TABLE I Percent Coating component: by weight Neoprene 45. Phenolic Resin45. 0 Linseed Oil 7. 0 Carbon Black 3. 0

The neoprene coating component imparts flexibility to the coating andgood aging characteristics, as well as being a film former, while thephenolic resin imparts toughness, and adhesiveness or tack to thecoating.

The linseed oil, which has a tendency to migrate to the surface of theapplied coating composition, acts as a release agent, facilitating theremoval of the finished film product from the surface of theadhesive-coated, raised pattern, without seriously impairing the filmbonding properties of the adhesive composition. The carbon-blackcomponent, which is dispersed .throughout the adhesive composition,functions to absorb incident infrared radiation. selectivelytransferring, by conduction, the resultant heat energy absorbed to thatportion of the film surface in contact with coated, raised, pattern 15.

The foregoing carbon-black adhesive mixture formulation is given merelyas an illustrative example of a type of adhesive system which isoperable in the present process. Numerous other adhesives may also beemployed, as would be apparent to those skilled in the art.

The thickness of the adhesive mixture which is applied to the surface ofraised pattern 15 may vary within wide limits dependent upon suchvariable factors as the specific adhesive formulation employed, thethicknesses of the thermoplastic films which are to be embossed and/orlaminated together, the intensity of the heat emanating from radiantheat energy source 16 and the rate of rotation of cylinder 14, forexample. Generally, the coating thickness may vary from about 0.5 mil toabout 50 mils and preferably from about mils to about 25 mils.

Raised pattern 15 may be formed on the surface of cylinder 14 using wellknown prior art techniques such as conventional engraving methodswhereby a series of intersecting raised lines in a predetermined patternmay be formed upon the surface of the cylinder. Another method which maybe employed to form the desired raised pattern upon the surface ofcylinder 14 is to utilize a precut pattern, fabricated from materialssuch as paperboard or the like, which is adhesively secured to thesurface of cylinder 14. In addition to performing quite satisfactorilyin the process of the present invention, this latter method of raisedpattern formation, i.e. utilizing a precut grid or pattern which isadhesively secured to a smooth surfaced cylinder, avoids the attendantexpenses which arise from the employment of costly engraved cylindermembers.

The embossed laminar thermoplastic material of the present invention isideally suited for man applications and in articular packagingapplications suc as overwrap matena or bag structures, for example. Abag structure, as illustrated in FIG. 11, fabricated from the embossedlaminar film produced in accordance with the instant process hasadvantages not found in typical prior art thermoplastic bagconstructions. Among these advantages are the ease with which the bagsthemselves may be opened. As a result of the lamination and embossmentof the component wall layers of the bag, the film loses much of itsinherent limpness becoming stiffer and easier to handle during openingand filling operations. In addition, the bags themselves possess thermalinsulation properties by virtue of the air encapsulated between thelayers of the laminar structure, making bags of this type useful in therefrigeration storage of fresh or frozen foods and the like. As shown inFIG. 11 the bags are formed of tubes of the thermoplastic film laminateof the present invention which are heat sealed along their bottom end.

As illustrated in FIG. 12 the bags, fabricated with the embossed,laminar film of the present process may also have sidewall gusetts 22which are commonly employed in this type, i.e. thermoplastic, bagconstruction.

Although the present invention has been described with preferredembodiments, it is to be understood that modifications and variationsmaybe resorted to, without departing from the spirit and scope of thisinvention, as those skilled in the art will readily understand. Suchvariations and modifications are considered to be within the purview andscope of the layers of thermoplastic film adjacent said intersectingheat t seal lines contain encapsulated air.

2. A thermoplastic bag, in accordance with claim 1, wherein saidflattened tube is gusetted.

